Radio receiving system



May 15, 1928. 1,669,893

F. P. BENJAMIN RADIO RECEIVING SYSTEM Filed Dec. 14, 1925 'einen un,

Patented May 15, 1928.

1,669,893 PATENT ori-fics..l

FRED PARKER BENJAMIN, OF WATSEKAK, ILLINOIS.

RADIO RECEIVING SYSTEM.

Applcationrled December 14,1925. Serial No. 75,425.

This invention relatesto radio receiving systems.

An important object of the invention is to improve the quality of reception by eliminating the usual howls, squeals and whistles often caused by the generation of eddy currents and also by the generation of har-y monies.

A further object is to accomplish the above results without introducing losses and withoutthe use of any neutralizing, balancing or bridging action or the like.

A still further object is to accomplish the desired 'results by increasing the efficiency of the action of the grids of electron vdischarge tubes by providing a freer flow Of current thereto whereby more accurate reception is obtained, the means employed being adapted t0 minimize thegenerationof eddy currents and to filter out substantially all harmonics. y

, Other objects and advantages of the invention will become apparent during the course of the following description. y

The single figure of the drawing is a diagrammatic view wherein for thepurpose of illustration the invention is shown as applied to a system embodying one stage of radio frequency and a detector.

Referring to the drawing the numeral 10 designates the usual antenna which is connected to a coil 11 at the upper end thereof, the lower end of the coil being grounded as at 12. The coil 11 constitutes the primary of a radio frequency transformer which includes a pair of secondary coils 13 and 14, as shown. The secondary coils are shown as being connected at one end, as at 15, and a lead wire 16 is connected from the secondary coils to the grid 17 of an electron discharge tube 18. The opposite end of the secondary coil 14 is connected to a lead wire 19, as shown, and a variable condenser 2() is connected across the leads 16 and 19, in the usual manner.

The usual A and B batteries 21 and 22 of suitable voltages are provided, and the negative lead 23 from the A battery is connected to one side of the tube filament 24. A lead 25 i-s connected between the positive side of the A battery and the negative side of the B battery in the usual manner, and current is supplied to the filament of the tube from the positive side of the A battery through a lead 26 in which 1S COnneCtd the usual rheostat 27. As clearly shown, the lead 19 from the secondary coil 14 is directly connected to the negative side of the iilament to constitute the grid return in the usual manner. The opposite side ofthe secondary coil 13 is connected to a lead 28 and a capacity is interposed between this lead y and tl e positive side of the A battery.

The stage of radio frequency described is coupled to the detector circuit to be described by a second transformer which includes a primary coil 30. One end of this coil is connected to the 'plate 31 of the tube 18 and the opposite end of the coil is connected by a lead 32 to the positive side of the B battery in the usual manner. AThe second transformer also includes a pair of secondary coils 33 and 34, as shown,and vthe coils are connected at one end as at 35. From the connection 35 a lead 36vis yconnected to the usual grid leak and condenser 37 and 38, from which a rlead 39 extends to the grid 40 of a'second electron discharge tube 41 which Y acts as the detector. The opposite'end of the coil 34 is connected by a lead 42 to the wire 19, and a variable. condenser 43 is connected across the leads 36 and-19. rlhe wire 19 also is connected to the negative side of the filament 44 of the Vtube 41.

The negative side of the A battery is connected with the negative side of the filament 44 through a lead 45, one end of which is connected to the wire 26 while the oppo site end is connectedto the usual rheostat 46. The opposite end of the secondary coil 43 connects with a lead 47 and a fixed capacity 48 is interposed between the lead 47 and the positive side of the filament 44.

The detector circuit aside from the scc` ondary coils of the transformer may be of any desired type and may employ a feed back coil 49 connected at one end to the plate 5() of thetube 41. The opposite end of the coil 49 will be connected bya lead 51 with onev terminal of the phones or speaker while the opposite terminal thereof will be connected by a wire with the positiveI side of the B battery.

It has been found that the provision of the dual coils of the transformer provides multiple grid returns permitting a freer flow of current to the grids of the tubes, thus materially reducing the generation of eddy currents and greatly improving the quality of reception. It is believed that the fixed,

condenser-s 29 and 4,8 act as filters to eliminate harmonics, and the general effect of the circuit described is to eliminate or greatly minimize the usual howls, squeals and Whistles. rI`hus only the desired reception is heard in the speaker, and the quality of this reception lis materially improved. v

The circuit illustrated is tobe w only as one embodiment of tlle invention, and it is to be understood that the connections of the leads from lthe secondaries of the transformersfto the iilaineiitsor' the tubes may be varied. In other \iords,the particular connections illustrated are not vital ,to the proper operation of the circuit, and the leads from the secondaries may be reversed or the fixed capacities 29 and 48 may be changed overto the negative leads of the lilanientgifdesired. The `capacities of the condensers 20 and 43. and the number ot turns of irire employed in making the transformers will of course, depend upon the range of frequencies which it is desired to receive. 'Ihe invention has beenr designed particularly foruse in connection With tuned radio frequency, but will operate eicicntly in connection with vother radio frequency types. The invention also is appli# cable to detector circuits as illustrated in the drawing and also tohdio frequency circuits. y It also has been found that the invention may be applied -either to one tube of a multi-tube circuit or may be applied to all of the tubes thereof.`

The use of the ilixed condensers in the grid return has been found4 important, but these condensers are 4not critical. `The secondaries of the transformers described may be ,wound independently upon their forms, or the secondaries of each transformer may be wound as a pair.

I claim:

1. In a radio receiving system including an electron discharge tube having a filament and grid therein, and a primary transformer coil, a pair of secondary transformer coils associated with said primary coil, one end of e'a'cli 3f-said secondary coils being connected considered to the grid of the tube, the other end of one of said secondary 'coils being connected to one end of the tube `filament, and a capacity connected between the other end of said secondary coil and the opposite end of said tube filament. y

2. The kcombination with a radio frequency circuit including an input coil, an electron discharge tibe having a filament and grid therein, and a variable capacity connected between said grid and one end of said filament, of a pair of secondary coils arranged in inductive relation to said input coil, one end of each of said secondary coils being connectcdto said grid, the ov posite end of one oft said secondary coils being connected to one end of said filament, and a fixed `capacity connected betiveeii the opposite end of the other of saidsecondary coils and the other end of said filament.

y3.111 a radio receiving system includingr an electron discharge tube having a filament and grid'therein and a primary transformer coil, a pair of secondary transformer coils inductively associated with said primary coil, one end of each of said secondary coils being connected to the grid of the tube, the other ends of said secondary Acoils being connected to the ends ofthe tube filament respectively, and a capacity connected in series with one of said secondary coils. y

In testimony whereof I'afiix my signature.

TREDPARKER BENJAMIN. 

